This invention relates to surveillance cameras and, in particular, to a method and apparatus for compensating the image blurring from a moving video surveillance camera.
Video surveillance systems generally use the interlacing method of displaying images to save the video bandwidth and still provide a smooth picture. In interlaced displays, the display alternates between drawing the even field, which consists of the even-numbered lines, and the odd field, which consists of the odd-numbered lines, of each frame. As used herein, frame consists of an even and odd field and refers to one of the still images, which make up the moving video. Similarly, the surveillance cameras used in these interlaced systems capture only half of the lines from each frame, i.e., one field at a time. The pairs of fields of each frame are perceived at the same time giving the appearance of a complete frame because of persistence of vision.
Video surveillance cameras that are movable, generally suffer degradation of the video when the camera is panned or tilted. The degradation blurs the video image and results in a dual image that has a ghost-like appearance. This undesirable blurring is most evident in images of static scenes viewed by a moving camera. Accordingly, there has been a long felt need in the industry for a video surveillance camera that has a minimal amount of blurring when the camera is moved.